Year	Percent of Total
1960-01-01	39.6790271055452
1961-01-01	39.9225821831465
1962-01-01	40.2655189028812
1963-01-01	40.6101720095764
1964-01-01	40.8326828396560
1965-01-01	40.8910668192841
1966-01-01	41.0366438684916
1967-01-01	40.9837089719393
1968-01-01	40.8095725351272
1969-01-01	40.6202220962612
1970-01-01	40.4609476065035
1971-01-01	40.3834553149414
1972-01-01	40.2895362772980
1973-01-01	40.1718905822364
1974-01-01	39.9965880822801
1975-01-01	39.7441167514590
1976-01-01	39.4837672412321
1977-01-01	39.1509269603016
1978-01-01	38.7608477260004
1979-01-01	38.3424495987065
1980-01-01	37.9188887921222
1981-01-01	37.5099977840176
1982-01-01	37.1248949713177
1983-01-01	36.7553663852908
1984-01-01	36.3926928356185
1985-01-01	36.0390042022866
1986-01-01	35.8250328895083
1987-01-01	35.6010304048942
1988-01-01	35.3729944196195
1989-01-01	35.1346055613443
1990-01-01	34.8791188746254
1991-01-01	34.7234387811281
1992-01-01	34.4658954040120
1993-01-01	34.1442370926377
1994-01-01	33.8056181421009
1995-01-01	33.4669190161584
1996-01-01	33.0023410304118
1997-01-01	32.6006458054906
1998-01-01	32.2066527777262
1999-01-01	31.7504854417802
2000-01-01	31.2119177189765
2001-01-01	30.7293829253598
2002-01-01	30.1758475164636
2003-01-01	29.5869996491777
2004-01-01	29.0285427193051
2005-01-01	28.5358601524094
2006-01-01	28.1425698726409
2007-01-01	27.7903833876281
2008-01-01	27.4830332422400
2009-01-01	27.2125154082528
2010-01-01	26.9730791427523
2011-01-01	26.7735123648440
2012-01-01	26.6025968714976
2013-01-01	26.4507948685489
2014-01-01	26.3018549238170
2015-01-01	26.1440992763512
2016-01-01	26.0018371672179
2017-01-01	25.8415019057289